Linear copolyesters of isophthalic acid 4,4&#39;-sulfonyldibenzoic acid, bis(4-beta-hydroxyethoxyphenyl) sulfone and ethylene glycol

ABSTRACT

Linear copolyesters are contemplated having the following repeating units: ##STR1## and ##STR2## and --O--CH 2  --CH 2  --O-- in their backbone structure. These polyesters have utility in the packaging industry for packaging various comestibles.

Cross References

The present application is related to application U.S. Ser. No. 690,483and U.S. Ser. No. 690,484.

The Invention

The present application is directed to polyester compositions and morespecifically to linear copolyester compositions formed from saturateddicarboxylic acids and saturated glycols; yet more particularly, theinvention is directed to packaging methods, and containers and packagesformed from these polyesters.

Presently there is a strong interest in protecting comestibles byenveloping these comestibles, for example foodstuffs, like carbonatedbeverages, medicines, and the like, in packages, for example moldedcontainers and, especially, biaxially oriented molded containers, whichpackages are formed from materials which comprise poly(ethyleneterephthalate). Such molded containers, whether they be biaxiallyoriented or unoriented possess many desirable characteristics forcertain products but there is a need to provide for a polyestercomposition which will have a glass transition temperature higher thanthat of poly(ethylene terephthalate) whereby containers made of such apolyester may be subjected to environments, for example highertemperatures, to which poly(ethylene terephthalate) may not besubjected. Additionally in order to achieve wider versatility in thetypes of products which are packaged therein, for example, comestibles,there is also a need to provide for polyester compositions which have anoxygen permeability which is lower than that of poly(ethyleneterephthalate). Additionally, many products, for example carbonatedbeverages, need to be packaged in containers having low carbon dioxidepermeability and accordingly there is also a need for providing forcontainers having carbon dioxide permeabilities which are lower thanthat of poly(ethylene terephthalate).

U.S. Pat. No. 2,593,411 suggests that polyesters may be formed fromdicarboxylic acids and from bis (4-beta-hydroxyalkoxyphenyl) sulfonesand that mixed polyesters can likewise be obtained by employing suchsulfones in combination with other dihydric and polyhydric alcohols.British Pat. Specification No. 678,264 suggests linear polyesters formedfrom an aromatic dicarboxylic acid and a glycol, e.g.bis(4-beta-hydroxyethoxyphenyl) sulfone. Also in this regard, referencemay be had to British Pat. Specification No. 1,196,911 which disclosesthe reaction of ethylene glycol with for example bis(4-chlorophenyl)sulfone and indicates that such type materials may be employed informing polyesters. Vol. 83 of Chemical Abstracts, No. 206808s (1975)discloses polyesters being formed from 4,4'-biphenyldicarboxylic acidand aliphatic glycols and bis(4-beta-hydroxyethoxyphenyl) sulfone.Similarly Vol. 83 Chemical Abstracts Nos. 165136a and 165644q (1975)disclose the use of such sulfones with napthalene dicarboxylic acids.None of the foregoing are directed to forming polyesters having oxygenpermeabilities and CO₂ permeabilities which are lower than that ofpoly(ethylene terephthalate) and which have glass transitiontemperatures higher than that of poly(ethylene terephthalate).

Japanese unexamined (Kokai) Patent Publication No. Showa 50-51595(Patent Application No. Showa 48-101837) discloses transparent,dimensionally stable, linear polyesters having high glass transitionpoints but has no recognition, or teachings, with regard to oxygenpermeability and carbon dioxide permeability. It is taught therein toemploy for example bis(4-beta-hydroxyethox phenyl) sulfone, alone orwith minor amounts of a glycol, and a dicarboxylic acid which isprimarily terephthalic acid. In order to obtain polyesters suitable forthe purposes of this patent application it is taught that, of thedicarboxylic acid, at least 70 mole percent, and preferably 80%, shouldbe terephthalic acid and, based on the acid employed, at least 60%, andpreferably 65-95%, should be the described sulfone. A wide variety ofoptional dicarboxylic acids which may be used in minor amounts are setforth from which it is possible to select isophthalic acid and sulfonyldibenzoic acid. Similarly a wide variety of diols are disclosed,including ethylene glycol.

The art is generally aware of the use of 4,4'-sulfonyldibenzoic acid, orits ester, or its halides, for use as a dicarboxylic acid in theformation of linear polyesters.

In accordance with the present invention applicant has satisfied a needin the art by providing for a linear copolyester which is the polymericreaction product of reactants consisting essentially of (A) isophthalicacid and 4,4'-sulfonyldibenzoic acid, and (B)bis(4-beta-hydroxyethoxyphenyl) sulfone and ethylene glycol. While thesepolyesters have numerous uses, by adjusting the amounts of the (A)reactants and the (B) reactants linear copolyesters can be formed havingoxygen permeabilities, carbon dioxide permeabilities, and glasstransition temperatures which will allow for their use in a wide varietyof applications in the packaging industry. Generally on a mole basis thecombined amounts of the (B) reactants above will be about 110 molepercent to about 300 mole percent of the combined amount of the (A)reactants.

For many applications in the packaging industry a copolyester havingquite advantageous properties will be formed wherein the (A) reactantsare present in an amount of about 15 mole percent to about 60 molepercent of 4,4'-sulfonyldibenzoic acid and about 85 mole percent toabout 40 mole percent of isophthalic acid, and the amount ofbis(4-beta-hydroxyethoxyphenyl) sulfone being between about 15% to about90% of the combined amounts of the (A) reactants, with the amounts ofthe (A) and (B) reactants being sufficient to provide an oxygenpermeability of less than that of poly- (ethylene terephthalate) and aglass transition temperature in excess of that of poly (ethyleneterephthaalate). The percentages are based on reactant feed. Preferably,the bis (4-beta-hydroxyethoxyphenyl) sulfone will be at least 50%relative to the combined amounts of the (A) reactants.

In passing it should be mentioned that when reference is made of oxygenand carbon dioxide permeability of poly(ethylene terephthalate) it isgenerally considered that the homopolymer has an oxygen permeability ofabout 8-9 cc. mil/100 in².day.atm. and a carbon dioxide permeability ofabout 62 cc.mil/100 in².day.atm. when measured on pressed films. In mycopending applications U.S. Ser. No. 643,282 and U.S. Ser. No. 643,283,reference is made to a carbon dioxide permeability of around 48 or 50.That figure is based on an extruded film and, as will be readilyapparent, extrusion effects some orientation which in turn has theeffect of reducing the permeability. Thus, the above figurescontemplate, as indicated, a pressed film which is substantiallyunoriented. Generally the glass transition temperature of unorientedpoly(ethylene terephthalate) is considered to be about 72°C.

Quite desirable linear copolyesters suitable for use in a wide varietyof applications in the packaging industry is a copolyester formed as thepolymeric reaction product in which the (A) reactants, on a mole basis,are about 45 to about 80% of isophthalic acid and about 20% to about 55%of 4,4'-sulfonyldibenzoic acid with the amount of thebis(4-betahydroxyethoxyphenyl) sulfone being about 60 mole percent toabout 85 mole percent of the combined amounts of the (A) reactants; suchpolyesters will have an oxygen permeability of less than about 7.4cc.mil/100 in².day.atm. (at about 50% relative humidity and about 73°F.) and a carbon dioxide permeability of less than about 65.6 cc.mil/100in².day.atm. (at about 50% relative humidity and about 73° F.) and glasstransition temperatures of at least about 121° C.

Quite outstanding polymers are formed as the reaction product whereinthe (A) reactants are about 60% to about 80% of isophthalic acid andabout 20% to about 40% of 4,4'-sulfonyldibenzoic acid with the amount ofbis(4-beta-hydroxyethoxphenyl) sulfone being between about 60% to about85% of the combined amount of the (A) reactants; such polymers will havea carbon dioxide permeability of less than about 50.3 and an oxygenpermeability of less than about 7.0 and a glass transition temperaturein excess of about 121° C. These polymers will be of outstanding utilityfor the packaging of carbonated beverages, i.e., pop, and exhibitexcellent heat stability.

As indicated the present invention also contemplates molded containerswhich are formed from materials which comprise linear copolyesters withthe copolyesters consisting essentially of the polymeric reactionproduct of the (A) and (B) reactants indicated hereinbefore. Biaxiallyoriented molded containers formed from the polyesters contemplatedherein are of especially outstanding characteristics. Packages whichcomprise comestibles, for example carbonated beverages, medicines, andthe like, enveloped in a molded container formed from materials whichcomprise a linear copolyester with the copolyester consistingessentially of the reaction product of the reactants indicated abovewill find utilization, and a flexibility of use, not possessed by thatof poly(ethylene terephthalate). The present application likewisecontemplates improvements in methods for protecting comestibles whereinthe comestibles are enveloped in packages which are formed from thecopolyesters contemplated herein.

When reference is made herein to bis(4-beta-hydroxy-ethoxyphenyl)sulfone and to ethylene glycol, it is contemplated that this likewiseincludes esters thereof as being employed for the reactants. Similarlywhen reference is made to isophthalic acid and to 4,4'-sulfonyldibenzoicacid that terminology likewise contemplates not only the acid but alsothe esters and acid halides thereof for use as reactants. Preferably inpracticing the invention the ethylene glycol andbis(4-beta-hydroxyethoxyphenyl) sulfone will be used as the diol per se,whereas the diesters of isophthalic acid and the 4,4'-sulfonyldibenzoicacid will be used as the (A) reactants. These esters may be thealiphatic esters or aromatic esters with the preferred esters being thealkyl esters having from about 1-4 carbon atoms, with methyl beingespecially highly preferred. The phenyl esters are the preferredaromatic esters.

The polyesters as contemplated herein are synthesized by methodsgenerally known in the art for producing polyesters. The reactants mayall be reacted in a single operation by first charging them to anappropriate reactor or a sequential operation may be employed by firstreacting isophthalic and ethylene glycol to form bis(beta-hydroxyethyl)isophthalate and then in turn reacting the latter with the remainingingredients. Since, as indicated, in the preferred practice the diestersof isophthalic acid and 4,4'-sulfonyldibenzoic acid will be employed,conventional transesterification followed by polycondensation iscontemplated as the preferred approach. Temperatures employed which willbe quite suitable for forming the polyesters will generally rangebetween about 200° or 210° up to about 295° C. or so, with the preferredranges being between about 225° to about 285° C. Of course the reactionwill be done under an inert atmosphere.

Conventional catalysts are likewise employed. For exampletransesterification is effected in the presence of effective catalyticamounts of transition metal compounds, alkaline earth metal compounds,or alkali metal compounds, for example the acetates, oxides, phenoxides,and alkoxides. Specific suitable catalysts will be, for example, zincacetate, manganese acetate, magnesium acetate, calcium acetate, andtitanium alkoxides, like titanium tetrabutoxides as well as mixed metalsalts for example potassium titanium oxalate. Suitable polycondensationcatalysts include, for example, antimony acetate, antimony trioxide,titanium alkoxide, and organotinoxides, for example stannous alkoxides.Usually the catalysts will be present in an amount of about 10⁻⁵ toabout 10⁻³ moles of catalysts per mole of total acid employed.

Of course suitable adjuvants, such as antioxidants and stabilizers maybe employed and they may be added directly to the reaction mass or addedto the final polymer.

The linear copolyesters contemplated herein may be formed into clearpackages, for example molded containers, and preferably biaxially moldedcontainers, using conventional plastic forming techniques such as, forexample, that disclosed in U.S. Pat. No. 3,733,309. These packages areideally suited for protecting foodstuffs, for example, carbonated softdrinks and beer, or medicines, or other related substances, by simplyenveloping those containers in these packages.

While the foregoing describes the present invention with sufficientparticularity to enable those skilled in the art to make and use samethere nonetheless follows, for exemplary purposes only, several specificexamples.

EXAMPLE 1

A linear polyester was prepared having the following units in itsbackbone: ##STR3## and ##STR4## The specific reactant materials employedin the feed stock was about 0.1 mole of an admixture of dimethylisophthalate (DMI) and dimethyl 4,4'-sulfonyldibenzoate acid(DMS) withthe former being present in an amount of about .08 mole and the latterin an amount of about 0.02 mole. About .20 mole of ethylene glycol (EG)and about 0.085 mole of bis(4-beta-hydroxyethoxyphenyl) sulfone (BSE)were employed as the glycol. Additionally about 6.5 × 10⁻⁵ mole of Sb₂O₃ and about 5 × 10⁻⁵ mole of Mn(C₂ H₃ O₂)₂.4H₂ O were employed forcatalytic purposes.

The mixture of the reactants along with the catalysts were weighed intoa 300 ml three-necked round bottom flask equipped with a stirrer,nitrogen inlet tube, and a condenser. The contents of the flask wereheated to and held at about 225° C. for about 3 hrs. with nitrogenflowing into the reaction flask to provide a nitrogen blanket and withmethanol being removed. The reactant system was then heated to about265° C. and held there for about 45 minutes during which time additionalmethanol was removed. A vacuum of about 0.2 to about 0.45 mm Hg was thenapplied and the reactants heated to between about 275° C. to about 285°C. with ethylene glycol being removed. The system was held at thatlatter temperature under that vacuum for approximately 6 hours afterwhich time the polymer was removed. Table A sets forth the glasstransition temperature of the polymer and as well as the carbon dioxideand oxygen permeability of films which were pressed from that polymer.The carbon dioxide permeability and the oxygen permeability weremeasured on pressed films employing ASTM D-1434-66 at a temperature ofabout 73° F. and 50% relative humidity and is in the units cc.mil/100in².day.atm. The glass transition temperature was measured with aDifferential Scanning Calorimeter. In Table A the percentages are basedon feed stock.

EXAMPLES 2-4

The procedure of Example 1 was substantially repeated using a totalmolar charge of the (A) reactants of about 0.1 mole with the molepercentage of the respective (A) constituents being varied as indicatedin Table A. Additionally, in Example 3 instead of employing 0.085 molesof BSE there was employed about 0.060 moles of BSE and about 0.19 molesof ethylene glycol.

                  TABLE A                                                         ______________________________________                                        Exam- %      %       %    Mole Ratio                                          ple   DMI    DMS     BSE  EG/BSE   O.sub.2                                                                            CO.sub.2                                                                           Tg                               ______________________________________                                        1     80     20      85   70/30    5.5  35.4 121° C.                   2     60     40      85   70/30    7.0  50.3 129° C.                   3     60     40      60   76/24    5.1  46   124° C.                   4     45     55      85   70/30    7.4  65.6 135° C.                   ______________________________________                                    

Following the know forming procedures of the prior art, for example U.S.Pat. No. 3,733,309, a biaxially oriented molded container (i.e., acontainer having a bottom wall and circumferential sidewall merging withand proceeding upwardly from the bottom wall, the sidewall at its uppermargin tapering inwardly and merging with a neck portion defining amouth opening) is formed fom the above polyesters of Examples 1-4. Thecontainers are clear and upon being filled with comestibles, forexample, foodstuffs like applesauce, medicines, and the like, so as toenvelope these substances, show outstanding characteristics for thepackaging of such products. The organic polymers of Examples 1-3 showparticularly outstanding characteristics for the packaging of carbonatedbeverages.

I claim:
 1. A linear copolyester suitable for use in the packaging of comestibles, said polyester being the polymeric reaction product of reactants consisting essentially of(A) isophthalic acid and 4,4'-sulfonyldibenzoic acid, and (B) bis(4-beta-hydroxyethoxyphenyl) sulfone and ethylene glycol.
 2. The copolyester of claim 1 wherein the combined amount of said B reactants are about 110 mole percent to about 300 mole percent of the combined amount of said A reactants.
 3. The copolyester of claim 2 wherein the molar amounts of said A reactants are about 45% to about 80% of isophthalic acid and about 20% to about 55% of 4,4'-sulfonyldibenzoic acid and the amount of said bis(4-beta-hydroxyethoxyphenyl) sulfone is about 60% to about 85% of the combined amount of said A reactants, said polyester having an O₂ permeability of less than about 7.4 cc.mil/100 in ².day.atm., a CO₂ permeability of less than about 65.6 cc.mil/100 in ².day.atm. and a glass transition temperature of at least about 121° C.
 4. The copolyester of claim 3, said polyester having a CO₂ permeability of less than about 50.3 cc.mil/100 in ².day.atm. and an O₂ permeability of less than about 7.0 cc.mil/100 in ².day.atm. and a glass transition temperature between about 121° to about 129° C., and A reactants being about 60% to 80% isophthalic acid and about 20% to 40% 4,4'-sulfonyldibenzoic acid.
 5. The copolyester of claim 2 wherein said A reactants are present in an amount of about 15% to about 60% 4,4'-sulfonyldibenzoic acid and about 85% to about 40% isophthalic acid and the amount of said bis(4-beta-hydroxyethoxyphenyl) sulfone is about 15% to about 90% of the combined amounts of said A reactants, the amounts of said A and B reactants being sufficient to provide an O₂ permeability of less than the of poly(ethylene terephthalate) and a glass transition temperature in excess of poly(ethylene terephthalate).
 6. A molded container formed from materials which comprise a linear copolyester, said copolyester being the copolyester of claim
 1. 7. A molded container formed from materials which comprise a linear copolyester, said copolyester being the copolyester of claim
 3. 8. A molded container formed from materials which comprise a lineaar copolyester, said copolyester being the copolyester of claim
 4. 9. A molded container formed from materials which comprise a linear copolyester, said copolyester being the copolyester of claim
 5. 10. The molded container of claim 6 wherein said container is a biaxially oriented container.
 11. A clear molded container formed from an organic polymer having an oxygen permeability of less than about 7.0 cc.mil/100 in². day.atm., a carbon dioxide permeability of less than about 50.3 cc.mil/100 in ².day.atm. and a glass transition temperature in excess of about 121° C. 